Method of preventing the rust-forming and adherence between friction material and opposite friction member
A method of preventing the rust-forming and adherence between friction material and opposite friction member by incorporating into the friction material a mixture or reaction product of boric acid and zinc oxide as an additive in an amount of 0.5 to 20 wt. %.
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The present invention relates to a method of preventing the rust-forming and adherence between friction material and opposite friction member.
Conventionally, the organic friction materials have been used as the friction materials for the brake or clutch of vehicles, which comprise mixtures of organic binder, reinforcement fibers such as asbestos, steel wool, glass fiber, rock wool, etc., friction modifier and the like, and the cast iron has been used in many cases as the opposite friction member.
These friction materials are used under every possible environments. For example, there is such a case as they are left alone for a long period of time at high temperature and high humidity in the rainy season or the like. In this case, there arise such problems as the rust-forming on the friction material and opposite friction member, the adherence between both materials resulting from said rust-forming, etc.
The invention solves these problems.
Also in the past, in the non-asbestos friction materials containing ferrous materials, such one as made to contain boric acid, phosphoric acid or salts thereof was proposed as an anti-rust agent in U.S. Pat. No. 4,363,884 for the prevention of the rust-forming and adherence of opposite friction member.
However, in the invention, the substance incorporated into the friction material as an additive are not the usual borates, such as borax, but a mixture of boric acid and zinc oxide or a reaction product of boric acid with zinc oxide.
SUMMARY OF THE INVENTIONThe gist of the invention lies in a method of preventing the rust-forming and adherence between friction material and opposite friction member characterized in that a mixture or reaction product of boric acid and zinc oxide is incorporated as an additive in an amount of 0.5 to 20 wt.% into the friction material. Rust-forming of cast iron, which is an opposite friction member, is thereby eliminated and adherence between the friction material and the opposite friction material resulting from the rust-forming is obviated.
DETAILED DESCRIPTION OF THE INVENTIONThe ratio of boric acid to zinc oxide in the mixture or the reaction product of boric acid with zinc oxide used in the invention can be set up in different ways depending on the object, but a range from 1/10 to 10/1 (by weight) is preferable.
Moreover, the amount of the mixture or the reaction product of boric acid and zinc oxide incorporated into the friction material is preferable 0.5 to 20 wt.%.
If less than 0.5% is incorporated, an insufficient improvement is realized, and, if more than 20% is incorporated, the increment in effect cannot be seen despite the increased amount that is incorporated.
The reaction product of boric acid with zinc oxide is a white powder with a melting point of about 930.degree. to 960.degree. C. which is obtained by allowing both to react at 500.degree. to 1000.degree. C. and which consists principally of zinc borate.
As described, the invention exerts an excellent improvement effect on the rust-forming and adherence between friction material and opposite friction member by the incorporation of a mixture or reaction product of boric acid and zinc oxide into the friction material.
EXAMPLETo the friction material of the basic formulation as shown in Table 1 were added mixtures or reaction products of boric acid and zinc oxide as shown in Table 2 and the friction materials were molded by the usual method to prepare the articles of the invention 1 through 5. Moreover, for comparison, the friction material was molded similarly starting from the basic formulation (without additive) to prepare the comparative article. Results obtained from the tests of rust-forming and adherent force thereof are shown in Table 2.
TABLE 1
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Basic formulation (Parts by weight)
Amount of
Material for formulation
formulation
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Binder Phenol resin
10
Reinforcement fiber
Asbestos 50
Friction modifier
Cashew dust 5
Barium sulfate
15
Graphite 15
Al.sub.2 O.sub.3 powder
3
Copper powder
15
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TABLE 2
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Article of
Article of
Article of
Article of
Article of
Comparative
Sample invention 1
invention 2
invention 3
invention 4
invention 5
article
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Additive Reaction product of
Mixture of boric acid
None
boric acid with
with zinc oxide
zinc oxide
Ratio: 71/29 Same as
1/10 1/1 10/1 --
boric acid/zinc oxide
left
Addition amount
1 20 5 5 5 --
(% by weight)
Rust-forming
Small Fine Small Small Small Middle to
large
Adherent force
0-1 0 4-6 4-8 5-7 8-15
kgf
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The conditions employed in the test methods of rust-forming and adherence aforementioned are as follows:
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Size of test piece 25 .times. 25 .times. 5 (mm)
Opposite member Cast iron
Areal press pressure
5 kg/cm.sup.2
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The values in Table 2 show the results obtained by storing the article for a week at high temperature and high humidity (50.degree. C., 95%) after having been dipped into distilled water. 9n
Claims
1. A method of preventing the rust-forming and adherence between friction material and opposite friction member characterized in incorporating into the friction material a mixture or reaction product of boric acid and zinc oxide wherein said boric acid and zinc oxide are present in a weight ratio of 1:10 to 10:1 as an additive in an amount of 0.5 to 20 wt.%.
2. The method according to claim 1, wherein the reaction product comprises essentially zinc borate.
| 4505963 | March 19, 1985 | Ogiwara |
| 3035100 | May 1981 | DEX |
| 56-161438 | December 1981 | JPX |
| 58-27772 | February 1983 | JPX |
| 58-77934 | May 1983 | JPX |
Type: Grant
Filed: Oct 21, 1986
Date of Patent: Nov 10, 1987
Assignees: Akebono Brake Industry Co., Ltd. (Tokyo), Akebono Research and Development Centre Ltd. (Hanyu)
Inventors: Kazuo Tsugawa (Gyoda), Susuma Wada (Tatebayashi)
Primary Examiner: Allan M. Lieberman
Law Firm: Oblon, Fisher, Spivak, McClelland & Maier
Application Number: 6/921,199
International Classification: C08J 514; C08K 322; C08K 338;
